Rhodium atom chemistry. 2. Interaction of small, well-defined rhodium clusters with dioxygen. Rh2(O2)n and Rh3(O2)m, Localized bonding models for dioxygen chemisorption on rhodium metal

Reactions of Laser-Ablated Rhodium Atoms with O2. Infrared Spectra and DFT Calculations for RhO, ORhO, (O2)RhO2, Rh2O2, Rh(O2) and (O2)Rh(O2) in Solid Argon

“…In fact, it is very interesting to note that the argon matrix spectra reported by Hanlan and Ozin 11,12 are very similar to our spectra with the major difference probably arising from their 10−12 K deposition temperature and our colder 7−8 K substrate. For this reason the complex bands reported at 922, 908, and 890 cm -1 are much larger relative to the 902 cm -1 band, , which is strong and sharp in the present experiments.…”

“…Over 10 bands are observed in the 1280−960 cm -1 region (Table ), with oxygen isotopic ratios appropriate for O−O stretching modes (near 1.059). These are undoubtedly due to various dioxygen complexes of rhodium atoms and small clusters as it has been shown that Rh atoms have an unusual propensity to form clusters. , Most of these bands were originally assigned by HO to specific dioxygen clusters, , but the present observations show that many of the original assignments are incorrect. Unfortunately the mixed and scrambled isotopic data are poor in this region and few definitive assignments can be made.…”

“…Isotopic data for this band demonstrate the primary involvement of one O 2 subunit with secondary coupling to other O 2 molecules. We note the absence of the 900 cm -1 band in pure dioxygen, , which apparently quenches thermal Rh and favors complex formation instead of the insertion reaction.…”

“…The bands at 923.0, 909.7, 900.1, and 890.7 cm -1 have been observed in a previous matrix isolation study of the reaction of thermal rhodium atoms and dioxygen by Hanlan and Ozin (HO), but were erroneously assigned to the O−O stretching modes of various dioxygen complexes, , despite the inappropriate oxygen isotopic ratios (1.045) for an O−O stretching mode. In this earlier work the metal atoms were produced thermally, and the fact that ORhO was still observed indicates that the insertion reaction occurs quite readily even with ground-state metal atoms.…”

“…This maximizes the interaction between rhodium and oxygen and shows the full extent of their chemistry under extreme conditions. The reaction of thermally generated rhodium atoms and dioxygen has been studied in inert matrixes previously, and numerous rhodium dioxygen species were identified; , however, many of these assignments are incorrect, as thermal rhodium atoms are much more reactive than anticipated. The results of the present work are discussed within the context of the cobalt and iridium dioxygen systems, which have already been studied in this laboratory, , and comparisons between the three systems are made.…”